Crest voltmeter



Feb. 14, 1950 c. w. RAlNEY 2,497,217?

CREST VOLTMETER Filed Feb. 19, 1947 POTENTIAL SOURCE G. W. RAINEY INVENTOR.

BY MM zam ATTORNEYS.

Patented Feb. 14 1956 UNITED STATES PATENT OFFICE CREST VOLTMETER Challenor W. Rainey, Ann Arbor, Mich., assignor to Ford Motor Company, Dearborn, Mich., a. corporation of Delaware Application February 19, 1947, Serial No. 729,617

2 Claims. 1 This invention relates to electrical testing apparatus; and, more particularly, to an adjustable spark gap of the type having utility in the testing of automotive ignition coils.

The routine testing of the eificiency of auto 2 appended claims and shown in the accompanying drawings, in which:

Figure 1 is a view, largely schematic, of the associated electrodes and the electrical wiring system.

motive ignition systems requires checking of .the Figure 2 is a plan view of the face of the inignition coil which forms a component of such strument taken as indicated by the line 2--2 of systems. This is customarily done through the Figure 3. use of an adjustable spark gap to determine the Figure 3 is a vertical transverse section through maximum air gap across which the coil will dis- 0 the instrument taken substantially as indicated charge as an indication of its operating characby the line 33 of the Figure 2. teristics. The measurement is not, of course, ex- Figure 4 is a longitudinal section through the tremely critical but is merely indicative of the collet on an enlarged scale. state of the coil. Nor is the equipment, cus- Referring first to Figure l, the essential comtomarily used in this operation, very complex or ponents of the device include a spherical elechighly accurate, since precision measurement of trode l0 and a torio electrode ll having a par- 3, high order is not required, Thus, a, number of tial web 12 in its lower section by means Of which adjustable spark gaps will occur to those versed it is mounted to the shaft l3 which is eccenin this art and most of them may be used with trically disposed with respect to the principal minor modification for this purpose. The difiiaxis of rotation of the tore indicated at [4. The culty in using such devices and the disadvantage Spherical electrode is mOunted On a p l5 which this invention is designed to overcome is which is slidably received in a Spring Collet that of keeping the spark gaps clean and in unithe pp portion of Which is of reduced thickform adjustment while in use. It will be underness and has a slot I! (see Figu flictionally stood that this is not the type of equipment which a g the pin I5 and tending hold it and is found, primarily, in laboratories; but which, the associated spherical electrode H] in any derather, is used in automotive garages where it is s e POSitiOn of adjustment n the 0 11 15. exposed to dust and dirt and considerable rough A typ electrical C uit S S own in Figure handling. It is imperative that the gap elec- 1, there being a current limiting resistor l8 introdes be accessible for easy and speedy cleanterposed between the spherical electrode l0 and ing to insure relative accuracy of results and that the terminal, l9 while the toric electrode II is they be maintained in proper relative position connected to'the second terminal 2i by the lead throughout the life of the apparatus. 22 and thence to the ground. It will be under- An advantage of this construction is that an stood that the high potential source to be tested adjustable spark gap has been devised in which is connected with the first and second coil terthe electrodes may be readily cleaned. A further minals I9 and 2! when the toric electrode H has advantage is that the electrodes may be autobeen rotated 180 from the position shown in matically locked in a predetermined zero posi- Figure l-thus obtaining the maximum spark tion after such cleaning without the exercise of gap, the high potential source is then activated any particular skill or care. Yet another advan- 40 and the toric electrode II is then rotated until tage of the construction is that the electrodes are discharge occurs between it and the spherical of such substantial size and disposition that deelectrode I0 indicating the maximum effective terioration of them in use is held to a minimum. spark gap and serving as an indication of the Another advantage which will appear to those crest voltage of the source. versed in the art is that the adjustable spark The device proper is shown in Figures 2 and 3 gap is extremely simple in operation and ecoand comprises a U-shaped base 25 which supnomical in manufacture. Another advantage is ports a panel 26 of insulating material arranged that, due to the shape of the electrodes, a preat an angle thereto for ease in reading. The ferred range of gap distances is obtained so that electrodes I0 and II are arranged beneath the quite precise readings are available through the panel 26, the shaft l3 supporting the toric eleccritical range of discharge. trode H extends through a bushing 27 supported Other advantages will be readily apparent to in the panel 26 and terminates in a control knob those familiar with the devices now in use in 28 on the upper surface of the panel and adapted this field by comparing them with the structure to indicate, by means of suitable graduations on described in this specification, claimed in the the face of the panel, the relative displacement 3 of the toric electrode H with respect to the spherical electrode Ill. The latter is slidably received in the collet l6 mounted in the boss 29 secured to the back of the panel 26 adjacent its upper edge and axially aligned with the principal plane of the toric electrode I l. A lead 3| extends from the collet l t9 the resistor lt and thence to the first coil terminal I9, while the st'rip lead 22 extends from the bushing 21 to the second coil terminal 2!. An opening 32 in the panel 25 provides visual access to the area of critical displacement between the two electrodes and per; mits observation of them to determine when dis:

charge occurs. A lens 33fi Jfhl iimtd in this opening to assist in this observation.

The operation of the device should be quite clear from the foregoing and attention isn'ow directed to the ease with which it may be cleaned and readjusted. The toric electrode may be readily detached from the "shaft l3 and its surface buffed to remove any accumulation of foreign matter or any inequalities diie to the arcing. At the same time the spheribal electrode in; may be withdrawn from the collet l6 and similarly treated. The resetting of the device isextremely easyand gives accurate r'sultse'ven though there has been considerable wear of either or both electrodes. To effect this, the pin I5 is reinserted in the collet l6 and the toric electrode H is reattached to the shaft 'l3 while the latter is rotated to a position substantially 180 from that shown in Figure 1 giving the maximum relative displacement. The spherical -electrode I0 is then pulled inwardlyi. e.*, towardthe shaft 13, so that it occupies a position substantiallymoreadvanced than it will have when in Contact with the toric electrode in the position 'ofminimum displacement. The shaft I3 is the'n'rotated 180 degrees to the position shown in Figure 1. This forces the spherical electrode I'll associated with the pin l5-outwardlyuntil it reaches the position shown in Figure 1 when the two electrodes are again in contact'in the position of minimum relative displacement. The spring "collet l6 secures the pin I5 in this position so that the s herical electrode is thereafter properlyheldat the j'zero point despite any diminution in dimension in either of the two co-op'erating elements. Thus,

it is extremely simple 'to clean the device and it may be reset with considerable accuracy "without the use of particular skill or measurements.

. The advantage of this construction "shouldbe quite clear to those who. know the practicable difliculties met in the maintenance-and operation of adjustable spark gaps in this 'particularfield.

It is to be observed that thedevi'ce is extremely sturdy and economical to 'manufactura'may be readily cleaned, and "easily reset to aproper adjustment with a minimumof time and skill.

It will be realized that certain changes may be made in the construction shown herein and it is the intention to cover by the claims such of these variations as are reasonably included within the scope thereof.

The invention claimed is:

l I n a variable spark gap, a panel, a shaft roeasements-din said panel; a first relatively movable electrode comprising a tore secured to one end of said shaft at a point spaced from the geometrical center of said tore, a second relativelyiixed spherical electrode mounted on a pin, said pin being slidably received in a sleeve mounted on panel and so disposed that the longitudinal 6; said pin substantially coincides with the "c'ipal plane of said tore and is normal ,toand intercepts said shaft, said sleeve includingresilient means engaging said pin and normally urging it to maintain a selected position therein, and indicating means on the face of said panel showing the relative displacement between said electrodes as said tore is rotated about the eccentric axisaffo'rded by said shaft.

2. In a variable spark gap, a panel, a shaft rotatably mounted in said panel, a first relatively movable electrode comprising a tore secured to one end of said shaft at a point spaced from the geometrica1 center of said tore, a second relatively fixed spherical electrode'm'ounted on a pin, said pin being slidably received in a sleeve mounted on said panel and so disposed that the longitudinal axis of said :pin substantially coincides with the principal 'pla'neof said tore and is normal to and'inter's'ects said shaft, said tore'and said spherical electrodev being arranged so that a complete revolution of the tore .will'cause the sphere to assume the correct position for operation, said sleeve including resilient means engaging said'pin and normally urging it to maintain a selected :position therein, and indicating means on the face of said panel showing the relative displacement betweensaid electrodes as said tore is rotated about the eccentric axis afforded by said shafti CHALLENOR W. RAINEY.

REFERENCES CITED The following 'references are of 'recordin the file of this "patent:

UNITED STATES PATENTS 

